SUDS
Sustainable Urban Drainage systems provide a method of dealing with surface water drainage and run-off. They aim to replicate nature's proven solutions, and have an important role to play in preventing flooding and pollution.
Common types of SUDS include:
Filer strips and Swales
CIRIA defines these as "vegetated surface features that drain water evenly off impermeable areas. Swales are long shallow channels whilst filter strips are gently sloping areas of ground." They are very economic drainage techniques, they can be a temporary or permanent measure, and are able to control an overflow of surface water on land that suffers from a gradient. As these systems mimic natural drainage patterns, they can be disguised with vegetation, so long as species which might erode them are not introduced.
Balancing Ponds
Artificially dug ponds which are designed to blend naturally with the landscape to provide a seamless rainwater drainage system. According to CIRIA, they are "designed to attenuate flows by storing runoff during the peak flow and releasing it at a controlled rate during and after the peak flow has passed." The ponds are often lined and can be arranged as a network to provide a system with which to filter the water. Gates can also be applied to help monitor the water level. Again, they offer a useful opportunity to create a wildlife habitat, and work well in open spaces.
Porous pavements
The composition is such that water is able to pass through the pavement, and during colder, wetter periods when freezing may occur, the damage that is often caused to traditional pavements is greatly reduced with a porous pavement.
CIRIA's website makes the important point that, "The water passes through the surface to the permeable fill. This allows the storage, treatment, transport and infiltration of water. Both the surface and the sub-base of a pavement must allow the passage of water - for this reason, porous asphalt laid on a conventional impermeable base is not a permeable pavement."
It should also be remembered that other types of naturally porous surface, such as grassland, can be part of SUDS.
Chartered Institution of Water and Environmental Management CIRIA Sustainable Urban Drainage Systems Network |
